For the air conditioning of motor vehicles, use is made of non-combustible refrigerants in order to avoid the risk of an explosion in the vehicle interior compartment in the event of an accident. The refrigerants that have hitherto been used have, however, either already been banned, or are at least regarded as problematic, owing to their high global warming potential. One possible environmentally compatible, non-combustible refrigerant is CO2 (R744), which has already partially replaced the previous refrigerants. CO2 air conditioning systems, however, operate with high operating pressures, which place particularly high demands on the strength and sealing action of the system components. The advantage associated with the high operating pressure consists in that, owing to the relatively high density of CO2, a lower volume flow rate is required to obtain a relatively high level of cooling power.
A scroll-type compressor for a CO2 vehicle air conditioning system is known from JP 2006/144635 A. In general, scroll-type compressors of said type have rotational-speed-regulated electric drives in order to control the refrigeration power of the compressor. In conjunction with vehicle air conditioning systems that operate with conventional, low-pressure refrigerants, scroll-type compressors of simple construction are also known in which power regulation is realized by virtue of the compressor being activated or deactivated.
Accordingly, U.S. Pat. No. 6,273,692 B1 discloses a scroll-type compressor having a mechanical drive which can be connected to the compressor unit by means of an electromagnetic clutch. Such clutches generally have a heavy steel disk. The mass moment of inertia is therefore high, which has a correspondingly adverse effect on fuel consumption. Furthermore, the clutch is an expensive component. US 2002/0081224 A1 discloses a variable low-pressure scroll-type compressor which can be activated and deactivated by means of a radial movement of one of the two scroll spirals. Here, the eccentricity between the two scroll spirals is eliminated, which scroll spirals accordingly pass out of engagement in the radial direction.